1 //===- lib/MC/WasmObjectWriter.cpp - Wasm File Writer ---------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements Wasm object file writer information.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/ADT/STLExtras.h"
15 #include "llvm/ADT/SmallPtrSet.h"
16 #include "llvm/BinaryFormat/Wasm.h"
17 #include "llvm/MC/MCAsmBackend.h"
18 #include "llvm/MC/MCAsmLayout.h"
19 #include "llvm/MC/MCAssembler.h"
20 #include "llvm/MC/MCContext.h"
21 #include "llvm/MC/MCExpr.h"
22 #include "llvm/MC/MCFixupKindInfo.h"
23 #include "llvm/MC/MCObjectWriter.h"
24 #include "llvm/MC/MCSectionWasm.h"
25 #include "llvm/MC/MCSymbolWasm.h"
26 #include "llvm/MC/MCValue.h"
27 #include "llvm/MC/MCWasmObjectWriter.h"
28 #include "llvm/Support/Casting.h"
29 #include "llvm/Support/Debug.h"
30 #include "llvm/Support/ErrorHandling.h"
31 #include "llvm/Support/LEB128.h"
32 #include "llvm/Support/StringSaver.h"
37 #define DEBUG_TYPE "mc"
41 // For patching purposes, we need to remember where each section starts, both
42 // for patching up the section size field, and for patching up references to
43 // locations within the section.
44 struct SectionBookkeeping {
45 // Where the size of the section is written.
47 // Where the contents of the section starts (after the header).
48 uint64_t ContentsOffset;
51 // The signature of a wasm function, in a struct capable of being used as a
53 struct WasmFunctionType {
54 // Support empty and tombstone instances, needed by DenseMap.
55 enum { Plain, Empty, Tombstone } State;
57 // The return types of the function.
58 SmallVector<wasm::ValType, 1> Returns;
60 // The parameter types of the function.
61 SmallVector<wasm::ValType, 4> Params;
63 WasmFunctionType() : State(Plain) {}
65 bool operator==(const WasmFunctionType &Other) const {
66 return State == Other.State && Returns == Other.Returns &&
67 Params == Other.Params;
71 // Traits for using WasmFunctionType in a DenseMap.
72 struct WasmFunctionTypeDenseMapInfo {
73 static WasmFunctionType getEmptyKey() {
74 WasmFunctionType FuncTy;
75 FuncTy.State = WasmFunctionType::Empty;
78 static WasmFunctionType getTombstoneKey() {
79 WasmFunctionType FuncTy;
80 FuncTy.State = WasmFunctionType::Tombstone;
83 static unsigned getHashValue(const WasmFunctionType &FuncTy) {
84 uintptr_t Value = FuncTy.State;
85 for (wasm::ValType Ret : FuncTy.Returns)
86 Value += DenseMapInfo<int32_t>::getHashValue(int32_t(Ret));
87 for (wasm::ValType Param : FuncTy.Params)
88 Value += DenseMapInfo<int32_t>::getHashValue(int32_t(Param));
91 static bool isEqual(const WasmFunctionType &LHS,
92 const WasmFunctionType &RHS) {
97 // A wasm data segment. A wasm binary contains only a single data section
98 // but that can contain many segments, each with their own virtual location
99 // in memory. Each MCSection data created by llvm is modeled as its own
100 // wasm data segment.
101 struct WasmDataSegment {
102 MCSectionWasm *Section;
107 SmallVector<char, 4> Data;
110 // A wasm import to be written into the import section.
112 StringRef ModuleName;
119 // A wasm function to be written into the function section.
120 struct WasmFunction {
122 const MCSymbolWasm *Sym;
125 // A wasm export to be written into the export section.
132 // A wasm global to be written into the global section.
137 uint64_t InitialValue;
138 uint32_t ImportIndex;
141 // Information about a single relocation.
142 struct WasmRelocationEntry {
143 uint64_t Offset; // Where is the relocation.
144 const MCSymbolWasm *Symbol; // The symbol to relocate with.
145 int64_t Addend; // A value to add to the symbol.
146 unsigned Type; // The type of the relocation.
147 const MCSectionWasm *FixupSection;// The section the relocation is targeting.
149 WasmRelocationEntry(uint64_t Offset, const MCSymbolWasm *Symbol,
150 int64_t Addend, unsigned Type,
151 const MCSectionWasm *FixupSection)
152 : Offset(Offset), Symbol(Symbol), Addend(Addend), Type(Type),
153 FixupSection(FixupSection) {}
155 bool hasAddend() const {
157 case wasm::R_WEBASSEMBLY_MEMORY_ADDR_LEB:
158 case wasm::R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
159 case wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32:
166 void print(raw_ostream &Out) const {
167 Out << "Off=" << Offset << ", Sym=" << *Symbol << ", Addend=" << Addend
169 << ", FixupSection=" << FixupSection->getSectionName();
172 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
173 LLVM_DUMP_METHOD void dump() const { print(dbgs()); }
178 raw_ostream &operator<<(raw_ostream &OS, const WasmRelocationEntry &Rel) {
184 class WasmObjectWriter : public MCObjectWriter {
185 /// Helper struct for containing some precomputed information on symbols.
186 struct WasmSymbolData {
187 const MCSymbolWasm *Symbol;
190 // Support lexicographic sorting.
191 bool operator<(const WasmSymbolData &RHS) const { return Name < RHS.Name; }
194 /// The target specific Wasm writer instance.
195 std::unique_ptr<MCWasmObjectTargetWriter> TargetObjectWriter;
197 // Relocations for fixing up references in the code section.
198 std::vector<WasmRelocationEntry> CodeRelocations;
200 // Relocations for fixing up references in the data section.
201 std::vector<WasmRelocationEntry> DataRelocations;
203 // Index values to use for fixing up call_indirect type indices.
204 // Maps function symbols to the index of the type of the function
205 DenseMap<const MCSymbolWasm *, uint32_t> TypeIndices;
206 // Maps function symbols to the table element index space. Used
207 // for TABLE_INDEX relocation types (i.e. address taken functions).
208 DenseMap<const MCSymbolWasm *, uint32_t> IndirectSymbolIndices;
209 // Maps function/global symbols to the function/global index space.
210 DenseMap<const MCSymbolWasm *, uint32_t> SymbolIndices;
212 DenseMap<WasmFunctionType, int32_t, WasmFunctionTypeDenseMapInfo>
214 SmallVector<WasmFunctionType, 4> FunctionTypes;
215 SmallVector<WasmGlobal, 4> Globals;
216 unsigned NumGlobalImports = 0;
218 // TargetObjectWriter wrappers.
219 bool is64Bit() const { return TargetObjectWriter->is64Bit(); }
220 unsigned getRelocType(const MCValue &Target, const MCFixup &Fixup) const {
221 return TargetObjectWriter->getRelocType(Target, Fixup);
224 void startSection(SectionBookkeeping &Section, unsigned SectionId,
225 const char *Name = nullptr);
226 void endSection(SectionBookkeeping &Section);
229 WasmObjectWriter(std::unique_ptr<MCWasmObjectTargetWriter> MOTW,
230 raw_pwrite_stream &OS)
231 : MCObjectWriter(OS, /*IsLittleEndian=*/true),
232 TargetObjectWriter(std::move(MOTW)) {}
235 ~WasmObjectWriter() override;
237 void reset() override {
238 CodeRelocations.clear();
239 DataRelocations.clear();
241 SymbolIndices.clear();
242 IndirectSymbolIndices.clear();
243 FunctionTypeIndices.clear();
244 FunctionTypes.clear();
246 MCObjectWriter::reset();
247 NumGlobalImports = 0;
250 void writeHeader(const MCAssembler &Asm);
252 void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
253 const MCFragment *Fragment, const MCFixup &Fixup,
254 MCValue Target, uint64_t &FixedValue) override;
256 void executePostLayoutBinding(MCAssembler &Asm,
257 const MCAsmLayout &Layout) override;
259 void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
261 void writeString(const StringRef Str) {
262 encodeULEB128(Str.size(), getStream());
266 void writeValueType(wasm::ValType Ty) {
267 encodeSLEB128(int32_t(Ty), getStream());
270 void writeTypeSection(ArrayRef<WasmFunctionType> FunctionTypes);
271 void writeImportSection(ArrayRef<WasmImport> Imports, uint32_t DataSize,
272 uint32_t NumElements);
273 void writeFunctionSection(ArrayRef<WasmFunction> Functions);
274 void writeGlobalSection();
275 void writeExportSection(ArrayRef<WasmExport> Exports);
276 void writeElemSection(ArrayRef<uint32_t> TableElems);
277 void writeCodeSection(const MCAssembler &Asm, const MCAsmLayout &Layout,
278 ArrayRef<WasmFunction> Functions);
279 void writeDataSection(ArrayRef<WasmDataSegment> Segments);
280 void writeNameSection(ArrayRef<WasmFunction> Functions,
281 ArrayRef<WasmImport> Imports,
282 uint32_t NumFuncImports);
283 void writeCodeRelocSection();
284 void writeDataRelocSection();
285 void writeLinkingMetaDataSection(
286 ArrayRef<WasmDataSegment> Segments, uint32_t DataSize,
287 const SmallVector<std::pair<StringRef, uint32_t>, 4> &SymbolFlags,
288 const SmallVector<std::pair<uint16_t, uint32_t>, 2> &InitFuncs);
290 uint32_t getProvisionalValue(const WasmRelocationEntry &RelEntry);
291 void applyRelocations(ArrayRef<WasmRelocationEntry> Relocations,
292 uint64_t ContentsOffset);
294 void writeRelocations(ArrayRef<WasmRelocationEntry> Relocations);
295 uint32_t getRelocationIndexValue(const WasmRelocationEntry &RelEntry);
296 uint32_t getFunctionType(const MCSymbolWasm& Symbol);
297 uint32_t registerFunctionType(const MCSymbolWasm& Symbol);
300 } // end anonymous namespace
302 WasmObjectWriter::~WasmObjectWriter() {}
304 // Write out a section header and a patchable section size field.
305 void WasmObjectWriter::startSection(SectionBookkeeping &Section,
308 assert((Name != nullptr) == (SectionId == wasm::WASM_SEC_CUSTOM) &&
309 "Only custom sections can have names");
311 DEBUG(dbgs() << "startSection " << SectionId << ": " << Name << "\n");
312 encodeULEB128(SectionId, getStream());
314 Section.SizeOffset = getStream().tell();
316 // The section size. We don't know the size yet, so reserve enough space
317 // for any 32-bit value; we'll patch it later.
318 encodeULEB128(UINT32_MAX, getStream());
320 // The position where the section starts, for measuring its size.
321 Section.ContentsOffset = getStream().tell();
323 // Custom sections in wasm also have a string identifier.
324 if (SectionId == wasm::WASM_SEC_CUSTOM) {
326 writeString(StringRef(Name));
330 // Now that the section is complete and we know how big it is, patch up the
331 // section size field at the start of the section.
332 void WasmObjectWriter::endSection(SectionBookkeeping &Section) {
333 uint64_t Size = getStream().tell() - Section.ContentsOffset;
334 if (uint32_t(Size) != Size)
335 report_fatal_error("section size does not fit in a uint32_t");
337 DEBUG(dbgs() << "endSection size=" << Size << "\n");
339 // Write the final section size to the payload_len field, which follows
340 // the section id byte.
342 unsigned SizeLen = encodeULEB128(Size, Buffer, 5);
343 assert(SizeLen == 5);
344 getStream().pwrite((char *)Buffer, SizeLen, Section.SizeOffset);
347 // Emit the Wasm header.
348 void WasmObjectWriter::writeHeader(const MCAssembler &Asm) {
349 writeBytes(StringRef(wasm::WasmMagic, sizeof(wasm::WasmMagic)));
350 writeLE32(wasm::WasmVersion);
353 void WasmObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
354 const MCAsmLayout &Layout) {
357 void WasmObjectWriter::recordRelocation(MCAssembler &Asm,
358 const MCAsmLayout &Layout,
359 const MCFragment *Fragment,
360 const MCFixup &Fixup, MCValue Target,
361 uint64_t &FixedValue) {
362 MCAsmBackend &Backend = Asm.getBackend();
363 bool IsPCRel = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
364 MCFixupKindInfo::FKF_IsPCRel;
365 const auto &FixupSection = cast<MCSectionWasm>(*Fragment->getParent());
366 uint64_t C = Target.getConstant();
367 uint64_t FixupOffset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
368 MCContext &Ctx = Asm.getContext();
370 // The .init_array isn't translated as data, so don't do relocations in it.
371 if (FixupSection.getSectionName().startswith(".init_array"))
374 if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
375 assert(RefB->getKind() == MCSymbolRefExpr::VK_None &&
376 "Should not have constructed this");
378 // Let A, B and C being the components of Target and R be the location of
379 // the fixup. If the fixup is not pcrel, we want to compute (A - B + C).
380 // If it is pcrel, we want to compute (A - B + C - R).
382 // In general, Wasm has no relocations for -B. It can only represent (A + C)
383 // or (A + C - R). If B = R + K and the relocation is not pcrel, we can
384 // replace B to implement it: (A - R - K + C)
388 "No relocation available to represent this relative expression");
392 const auto &SymB = cast<MCSymbolWasm>(RefB->getSymbol());
394 if (SymB.isUndefined()) {
395 Ctx.reportError(Fixup.getLoc(),
396 Twine("symbol '") + SymB.getName() +
397 "' can not be undefined in a subtraction expression");
401 assert(!SymB.isAbsolute() && "Should have been folded");
402 const MCSection &SecB = SymB.getSection();
403 if (&SecB != &FixupSection) {
404 Ctx.reportError(Fixup.getLoc(),
405 "Cannot represent a difference across sections");
409 uint64_t SymBOffset = Layout.getSymbolOffset(SymB);
410 uint64_t K = SymBOffset - FixupOffset;
415 // We either rejected the fixup or folded B into C at this point.
416 const MCSymbolRefExpr *RefA = Target.getSymA();
417 const auto *SymA = RefA ? cast<MCSymbolWasm>(&RefA->getSymbol()) : nullptr;
419 if (SymA && SymA->isVariable()) {
420 const MCExpr *Expr = SymA->getVariableValue();
421 const auto *Inner = cast<MCSymbolRefExpr>(Expr);
422 if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF)
423 llvm_unreachable("weakref used in reloc not yet implemented");
426 // Put any constant offset in an addend. Offsets can be negative, and
427 // LLVM expects wrapping, in contrast to wasm's immediates which can't
428 // be negative and don't wrap.
432 SymA->setUsedInReloc();
437 unsigned Type = getRelocType(Target, Fixup);
439 WasmRelocationEntry Rec(FixupOffset, SymA, C, Type, &FixupSection);
440 DEBUG(dbgs() << "WasmReloc: " << Rec << "\n");
442 if (FixupSection.isWasmData())
443 DataRelocations.push_back(Rec);
444 else if (FixupSection.getKind().isText())
445 CodeRelocations.push_back(Rec);
446 else if (!FixupSection.getKind().isMetadata())
447 // TODO(sbc): Add support for debug sections.
448 llvm_unreachable("unexpected section type");
451 // Write X as an (unsigned) LEB value at offset Offset in Stream, padded
452 // to allow patching.
454 WritePatchableLEB(raw_pwrite_stream &Stream, uint32_t X, uint64_t Offset) {
456 unsigned SizeLen = encodeULEB128(X, Buffer, 5);
457 assert(SizeLen == 5);
458 Stream.pwrite((char *)Buffer, SizeLen, Offset);
461 // Write X as an signed LEB value at offset Offset in Stream, padded
462 // to allow patching.
464 WritePatchableSLEB(raw_pwrite_stream &Stream, int32_t X, uint64_t Offset) {
466 unsigned SizeLen = encodeSLEB128(X, Buffer, 5);
467 assert(SizeLen == 5);
468 Stream.pwrite((char *)Buffer, SizeLen, Offset);
471 // Write X as a plain integer value at offset Offset in Stream.
472 static void WriteI32(raw_pwrite_stream &Stream, uint32_t X, uint64_t Offset) {
474 support::endian::write32le(Buffer, X);
475 Stream.pwrite((char *)Buffer, sizeof(Buffer), Offset);
478 static const MCSymbolWasm* ResolveSymbol(const MCSymbolWasm& Symbol) {
479 if (Symbol.isVariable()) {
480 const MCExpr *Expr = Symbol.getVariableValue();
481 auto *Inner = cast<MCSymbolRefExpr>(Expr);
482 return cast<MCSymbolWasm>(&Inner->getSymbol());
487 // Compute a value to write into the code at the location covered
488 // by RelEntry. This value isn't used by the static linker, since
489 // we have addends; it just serves to make the code more readable
490 // and to make standalone wasm modules directly usable.
492 WasmObjectWriter::getProvisionalValue(const WasmRelocationEntry &RelEntry) {
493 const MCSymbolWasm *Sym = ResolveSymbol(*RelEntry.Symbol);
495 // For undefined symbols, use a hopefully invalid value.
496 if (!Sym->isDefined(/*SetUsed=*/false))
499 uint32_t GlobalIndex = SymbolIndices[Sym];
500 const WasmGlobal& Global = Globals[GlobalIndex - NumGlobalImports];
501 uint64_t Address = Global.InitialValue + RelEntry.Addend;
503 // Ignore overflow. LLVM allows address arithmetic to silently wrap.
504 uint32_t Value = Address;
509 static void addData(SmallVectorImpl<char> &DataBytes,
510 MCSectionWasm &DataSection) {
511 DEBUG(errs() << "addData: " << DataSection.getSectionName() << "\n");
513 DataBytes.resize(alignTo(DataBytes.size(), DataSection.getAlignment()));
515 size_t LastFragmentSize = 0;
516 for (const MCFragment &Frag : DataSection) {
517 if (Frag.hasInstructions())
518 report_fatal_error("only data supported in data sections");
520 if (auto *Align = dyn_cast<MCAlignFragment>(&Frag)) {
521 if (Align->getValueSize() != 1)
522 report_fatal_error("only byte values supported for alignment");
523 // If nops are requested, use zeros, as this is the data section.
524 uint8_t Value = Align->hasEmitNops() ? 0 : Align->getValue();
525 uint64_t Size = std::min<uint64_t>(alignTo(DataBytes.size(),
526 Align->getAlignment()),
528 Align->getMaxBytesToEmit());
529 DataBytes.resize(Size, Value);
530 } else if (auto *Fill = dyn_cast<MCFillFragment>(&Frag)) {
531 DataBytes.insert(DataBytes.end(), Fill->getSize(), Fill->getValue());
533 const auto &DataFrag = cast<MCDataFragment>(Frag);
534 const SmallVectorImpl<char> &Contents = DataFrag.getContents();
536 DataBytes.insert(DataBytes.end(), Contents.begin(), Contents.end());
537 LastFragmentSize = Contents.size();
541 // Don't allow empty segments, or segments that end with zero-sized
542 // fragment, otherwise the linker cannot map symbols to a unique
543 // data segment. This can be triggered by zero-sized structs
544 // See: test/MC/WebAssembly/bss.ll
545 if (LastFragmentSize == 0)
546 DataBytes.resize(DataBytes.size() + 1);
547 DEBUG(dbgs() << "addData -> " << DataBytes.size() << "\n");
550 uint32_t WasmObjectWriter::getRelocationIndexValue(
551 const WasmRelocationEntry &RelEntry) {
552 switch (RelEntry.Type) {
553 case wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB:
554 case wasm::R_WEBASSEMBLY_TABLE_INDEX_I32:
555 if (!IndirectSymbolIndices.count(RelEntry.Symbol))
556 report_fatal_error("symbol not found in table index space: " +
557 RelEntry.Symbol->getName());
558 return IndirectSymbolIndices[RelEntry.Symbol];
559 case wasm::R_WEBASSEMBLY_FUNCTION_INDEX_LEB:
560 case wasm::R_WEBASSEMBLY_GLOBAL_INDEX_LEB:
561 case wasm::R_WEBASSEMBLY_MEMORY_ADDR_LEB:
562 case wasm::R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
563 case wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32:
564 if (!SymbolIndices.count(RelEntry.Symbol))
565 report_fatal_error("symbol not found in function/global index space: " +
566 RelEntry.Symbol->getName());
567 return SymbolIndices[RelEntry.Symbol];
568 case wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB:
569 if (!TypeIndices.count(RelEntry.Symbol))
570 report_fatal_error("symbol not found in type index space: " +
571 RelEntry.Symbol->getName());
572 return TypeIndices[RelEntry.Symbol];
574 llvm_unreachable("invalid relocation type");
578 // Apply the portions of the relocation records that we can handle ourselves
580 void WasmObjectWriter::applyRelocations(
581 ArrayRef<WasmRelocationEntry> Relocations, uint64_t ContentsOffset) {
582 raw_pwrite_stream &Stream = getStream();
583 for (const WasmRelocationEntry &RelEntry : Relocations) {
584 uint64_t Offset = ContentsOffset +
585 RelEntry.FixupSection->getSectionOffset() +
588 DEBUG(dbgs() << "applyRelocation: " << RelEntry << "\n");
589 switch (RelEntry.Type) {
590 case wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB:
591 case wasm::R_WEBASSEMBLY_FUNCTION_INDEX_LEB:
592 case wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB:
593 case wasm::R_WEBASSEMBLY_GLOBAL_INDEX_LEB: {
594 uint32_t Index = getRelocationIndexValue(RelEntry);
595 WritePatchableSLEB(Stream, Index, Offset);
598 case wasm::R_WEBASSEMBLY_TABLE_INDEX_I32: {
599 uint32_t Index = getRelocationIndexValue(RelEntry);
600 WriteI32(Stream, Index, Offset);
603 case wasm::R_WEBASSEMBLY_MEMORY_ADDR_SLEB: {
604 uint32_t Value = getProvisionalValue(RelEntry);
605 WritePatchableSLEB(Stream, Value, Offset);
608 case wasm::R_WEBASSEMBLY_MEMORY_ADDR_LEB: {
609 uint32_t Value = getProvisionalValue(RelEntry);
610 WritePatchableLEB(Stream, Value, Offset);
613 case wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32: {
614 uint32_t Value = getProvisionalValue(RelEntry);
615 WriteI32(Stream, Value, Offset);
619 llvm_unreachable("invalid relocation type");
624 // Write out the portions of the relocation records that the linker will
626 void WasmObjectWriter::writeRelocations(
627 ArrayRef<WasmRelocationEntry> Relocations) {
628 raw_pwrite_stream &Stream = getStream();
629 for (const WasmRelocationEntry& RelEntry : Relocations) {
631 uint64_t Offset = RelEntry.Offset +
632 RelEntry.FixupSection->getSectionOffset();
633 uint32_t Index = getRelocationIndexValue(RelEntry);
635 encodeULEB128(RelEntry.Type, Stream);
636 encodeULEB128(Offset, Stream);
637 encodeULEB128(Index, Stream);
638 if (RelEntry.hasAddend())
639 encodeSLEB128(RelEntry.Addend, Stream);
643 void WasmObjectWriter::writeTypeSection(
644 ArrayRef<WasmFunctionType> FunctionTypes) {
645 if (FunctionTypes.empty())
648 SectionBookkeeping Section;
649 startSection(Section, wasm::WASM_SEC_TYPE);
651 encodeULEB128(FunctionTypes.size(), getStream());
653 for (const WasmFunctionType &FuncTy : FunctionTypes) {
654 encodeSLEB128(wasm::WASM_TYPE_FUNC, getStream());
655 encodeULEB128(FuncTy.Params.size(), getStream());
656 for (wasm::ValType Ty : FuncTy.Params)
658 encodeULEB128(FuncTy.Returns.size(), getStream());
659 for (wasm::ValType Ty : FuncTy.Returns)
666 void WasmObjectWriter::writeImportSection(ArrayRef<WasmImport> Imports,
668 uint32_t NumElements) {
672 uint32_t NumPages = (DataSize + wasm::WasmPageSize - 1) / wasm::WasmPageSize;
674 SectionBookkeeping Section;
675 startSection(Section, wasm::WASM_SEC_IMPORT);
677 encodeULEB128(Imports.size(), getStream());
678 for (const WasmImport &Import : Imports) {
679 writeString(Import.ModuleName);
680 writeString(Import.FieldName);
682 encodeULEB128(Import.Kind, getStream());
684 switch (Import.Kind) {
685 case wasm::WASM_EXTERNAL_FUNCTION:
686 encodeULEB128(Import.Type, getStream());
688 case wasm::WASM_EXTERNAL_GLOBAL:
689 encodeSLEB128(int32_t(Import.Type), getStream());
690 encodeULEB128(int32_t(Import.IsMutable), getStream());
692 case wasm::WASM_EXTERNAL_MEMORY:
693 encodeULEB128(0, getStream()); // flags
694 encodeULEB128(NumPages, getStream()); // initial
696 case wasm::WASM_EXTERNAL_TABLE:
697 encodeSLEB128(int32_t(Import.Type), getStream());
698 encodeULEB128(0, getStream()); // flags
699 encodeULEB128(NumElements, getStream()); // initial
702 llvm_unreachable("unsupported import kind");
709 void WasmObjectWriter::writeFunctionSection(ArrayRef<WasmFunction> Functions) {
710 if (Functions.empty())
713 SectionBookkeeping Section;
714 startSection(Section, wasm::WASM_SEC_FUNCTION);
716 encodeULEB128(Functions.size(), getStream());
717 for (const WasmFunction &Func : Functions)
718 encodeULEB128(Func.Type, getStream());
723 void WasmObjectWriter::writeGlobalSection() {
727 SectionBookkeeping Section;
728 startSection(Section, wasm::WASM_SEC_GLOBAL);
730 encodeULEB128(Globals.size(), getStream());
731 for (const WasmGlobal &Global : Globals) {
732 writeValueType(Global.Type);
733 write8(Global.IsMutable);
735 if (Global.HasImport) {
736 assert(Global.InitialValue == 0);
737 write8(wasm::WASM_OPCODE_GET_GLOBAL);
738 encodeULEB128(Global.ImportIndex, getStream());
740 assert(Global.ImportIndex == 0);
741 write8(wasm::WASM_OPCODE_I32_CONST);
742 encodeSLEB128(Global.InitialValue, getStream()); // offset
744 write8(wasm::WASM_OPCODE_END);
750 void WasmObjectWriter::writeExportSection(ArrayRef<WasmExport> Exports) {
754 SectionBookkeeping Section;
755 startSection(Section, wasm::WASM_SEC_EXPORT);
757 encodeULEB128(Exports.size(), getStream());
758 for (const WasmExport &Export : Exports) {
759 writeString(Export.FieldName);
760 encodeSLEB128(Export.Kind, getStream());
761 encodeULEB128(Export.Index, getStream());
767 void WasmObjectWriter::writeElemSection(ArrayRef<uint32_t> TableElems) {
768 if (TableElems.empty())
771 SectionBookkeeping Section;
772 startSection(Section, wasm::WASM_SEC_ELEM);
774 encodeULEB128(1, getStream()); // number of "segments"
775 encodeULEB128(0, getStream()); // the table index
777 // init expr for starting offset
778 write8(wasm::WASM_OPCODE_I32_CONST);
779 encodeSLEB128(0, getStream());
780 write8(wasm::WASM_OPCODE_END);
782 encodeULEB128(TableElems.size(), getStream());
783 for (uint32_t Elem : TableElems)
784 encodeULEB128(Elem, getStream());
789 void WasmObjectWriter::writeCodeSection(const MCAssembler &Asm,
790 const MCAsmLayout &Layout,
791 ArrayRef<WasmFunction> Functions) {
792 if (Functions.empty())
795 SectionBookkeeping Section;
796 startSection(Section, wasm::WASM_SEC_CODE);
798 encodeULEB128(Functions.size(), getStream());
800 for (const WasmFunction &Func : Functions) {
801 auto &FuncSection = static_cast<MCSectionWasm &>(Func.Sym->getSection());
804 if (!Func.Sym->getSize()->evaluateAsAbsolute(Size, Layout))
805 report_fatal_error(".size expression must be evaluatable");
807 encodeULEB128(Size, getStream());
808 FuncSection.setSectionOffset(getStream().tell() - Section.ContentsOffset);
809 Asm.writeSectionData(&FuncSection, Layout);
813 applyRelocations(CodeRelocations, Section.ContentsOffset);
818 void WasmObjectWriter::writeDataSection(ArrayRef<WasmDataSegment> Segments) {
819 if (Segments.empty())
822 SectionBookkeeping Section;
823 startSection(Section, wasm::WASM_SEC_DATA);
825 encodeULEB128(Segments.size(), getStream()); // count
827 for (const WasmDataSegment & Segment : Segments) {
828 encodeULEB128(0, getStream()); // memory index
829 write8(wasm::WASM_OPCODE_I32_CONST);
830 encodeSLEB128(Segment.Offset, getStream()); // offset
831 write8(wasm::WASM_OPCODE_END);
832 encodeULEB128(Segment.Data.size(), getStream()); // size
833 Segment.Section->setSectionOffset(getStream().tell() - Section.ContentsOffset);
834 writeBytes(Segment.Data); // data
838 applyRelocations(DataRelocations, Section.ContentsOffset);
843 void WasmObjectWriter::writeNameSection(
844 ArrayRef<WasmFunction> Functions,
845 ArrayRef<WasmImport> Imports,
846 unsigned NumFuncImports) {
847 uint32_t TotalFunctions = NumFuncImports + Functions.size();
848 if (TotalFunctions == 0)
851 SectionBookkeeping Section;
852 startSection(Section, wasm::WASM_SEC_CUSTOM, "name");
853 SectionBookkeeping SubSection;
854 startSection(SubSection, wasm::WASM_NAMES_FUNCTION);
856 encodeULEB128(TotalFunctions, getStream());
858 for (const WasmImport &Import : Imports) {
859 if (Import.Kind == wasm::WASM_EXTERNAL_FUNCTION) {
860 encodeULEB128(Index, getStream());
861 writeString(Import.FieldName);
865 for (const WasmFunction &Func : Functions) {
866 encodeULEB128(Index, getStream());
867 writeString(Func.Sym->getName());
871 endSection(SubSection);
875 void WasmObjectWriter::writeCodeRelocSection() {
876 // See: https://github.com/WebAssembly/tool-conventions/blob/master/Linking.md
877 // for descriptions of the reloc sections.
879 if (CodeRelocations.empty())
882 SectionBookkeeping Section;
883 startSection(Section, wasm::WASM_SEC_CUSTOM, "reloc.CODE");
885 encodeULEB128(wasm::WASM_SEC_CODE, getStream());
886 encodeULEB128(CodeRelocations.size(), getStream());
888 writeRelocations(CodeRelocations);
893 void WasmObjectWriter::writeDataRelocSection() {
894 // See: https://github.com/WebAssembly/tool-conventions/blob/master/Linking.md
895 // for descriptions of the reloc sections.
897 if (DataRelocations.empty())
900 SectionBookkeeping Section;
901 startSection(Section, wasm::WASM_SEC_CUSTOM, "reloc.DATA");
903 encodeULEB128(wasm::WASM_SEC_DATA, getStream());
904 encodeULEB128(DataRelocations.size(), getStream());
906 writeRelocations(DataRelocations);
911 void WasmObjectWriter::writeLinkingMetaDataSection(
912 ArrayRef<WasmDataSegment> Segments, uint32_t DataSize,
913 const SmallVector<std::pair<StringRef, uint32_t>, 4> &SymbolFlags,
914 const SmallVector<std::pair<uint16_t, uint32_t>, 2> &InitFuncs) {
915 SectionBookkeeping Section;
916 startSection(Section, wasm::WASM_SEC_CUSTOM, "linking");
917 SectionBookkeeping SubSection;
919 if (SymbolFlags.size() != 0) {
920 startSection(SubSection, wasm::WASM_SYMBOL_INFO);
921 encodeULEB128(SymbolFlags.size(), getStream());
922 for (auto Pair: SymbolFlags) {
923 writeString(Pair.first);
924 encodeULEB128(Pair.second, getStream());
926 endSection(SubSection);
930 startSection(SubSection, wasm::WASM_DATA_SIZE);
931 encodeULEB128(DataSize, getStream());
932 endSection(SubSection);
935 if (Segments.size()) {
936 startSection(SubSection, wasm::WASM_SEGMENT_INFO);
937 encodeULEB128(Segments.size(), getStream());
938 for (const WasmDataSegment &Segment : Segments) {
939 writeString(Segment.Name);
940 encodeULEB128(Segment.Alignment, getStream());
941 encodeULEB128(Segment.Flags, getStream());
943 endSection(SubSection);
946 if (!InitFuncs.empty()) {
947 startSection(SubSection, wasm::WASM_INIT_FUNCS);
948 encodeULEB128(InitFuncs.size(), getStream());
949 for (auto &StartFunc : InitFuncs) {
950 encodeULEB128(StartFunc.first, getStream()); // priority
951 encodeULEB128(StartFunc.second, getStream()); // function index
953 endSection(SubSection);
959 uint32_t WasmObjectWriter::getFunctionType(const MCSymbolWasm& Symbol) {
960 assert(Symbol.isFunction());
961 assert(TypeIndices.count(&Symbol));
962 return TypeIndices[&Symbol];
965 uint32_t WasmObjectWriter::registerFunctionType(const MCSymbolWasm& Symbol) {
966 assert(Symbol.isFunction());
969 const MCSymbolWasm* ResolvedSym = ResolveSymbol(Symbol);
970 F.Returns = ResolvedSym->getReturns();
971 F.Params = ResolvedSym->getParams();
974 FunctionTypeIndices.insert(std::make_pair(F, FunctionTypes.size()));
976 FunctionTypes.push_back(F);
977 TypeIndices[&Symbol] = Pair.first->second;
979 DEBUG(dbgs() << "registerFunctionType: " << Symbol << " new:" << Pair.second << "\n");
980 DEBUG(dbgs() << " -> type index: " << Pair.first->second << "\n");
981 return Pair.first->second;
984 void WasmObjectWriter::writeObject(MCAssembler &Asm,
985 const MCAsmLayout &Layout) {
986 DEBUG(dbgs() << "WasmObjectWriter::writeObject\n");
987 MCContext &Ctx = Asm.getContext();
988 wasm::ValType PtrType = is64Bit() ? wasm::ValType::I64 : wasm::ValType::I32;
990 // Collect information from the available symbols.
991 SmallVector<WasmFunction, 4> Functions;
992 SmallVector<uint32_t, 4> TableElems;
993 SmallVector<WasmImport, 4> Imports;
994 SmallVector<WasmExport, 4> Exports;
995 SmallVector<std::pair<StringRef, uint32_t>, 4> SymbolFlags;
996 SmallVector<std::pair<uint16_t, uint32_t>, 2> InitFuncs;
997 unsigned NumFuncImports = 0;
998 SmallVector<WasmDataSegment, 4> DataSegments;
999 uint32_t DataSize = 0;
1001 // In the special .global_variables section, we've encoded global
1002 // variables used by the function. Translate them into the Globals
1004 MCSectionWasm *GlobalVars =
1005 Ctx.getWasmSection(".global_variables", SectionKind::getMetadata());
1006 if (!GlobalVars->getFragmentList().empty()) {
1007 if (GlobalVars->getFragmentList().size() != 1)
1008 report_fatal_error("only one .global_variables fragment supported");
1009 const MCFragment &Frag = *GlobalVars->begin();
1010 if (Frag.hasInstructions() || Frag.getKind() != MCFragment::FT_Data)
1011 report_fatal_error("only data supported in .global_variables");
1012 const auto &DataFrag = cast<MCDataFragment>(Frag);
1013 if (!DataFrag.getFixups().empty())
1014 report_fatal_error("fixups not supported in .global_variables");
1015 const SmallVectorImpl<char> &Contents = DataFrag.getContents();
1016 for (const uint8_t *p = (const uint8_t *)Contents.data(),
1017 *end = (const uint8_t *)Contents.data() + Contents.size();
1021 report_fatal_error("truncated global variable encoding");
1022 G.Type = wasm::ValType(int8_t(*p++));
1023 G.IsMutable = bool(*p++);
1024 G.HasImport = bool(*p++);
1029 Import.ModuleName = (const char *)p;
1030 const uint8_t *nul = (const uint8_t *)memchr(p, '\0', end - p);
1032 report_fatal_error("global module name must be nul-terminated");
1034 nul = (const uint8_t *)memchr(p, '\0', end - p);
1036 report_fatal_error("global base name must be nul-terminated");
1037 Import.FieldName = (const char *)p;
1040 Import.Kind = wasm::WASM_EXTERNAL_GLOBAL;
1041 Import.Type = int32_t(G.Type);
1043 G.ImportIndex = NumGlobalImports;
1046 Imports.push_back(Import);
1049 G.InitialValue = decodeSLEB128(p, &n);
1051 if ((ptrdiff_t)n > end - p)
1052 report_fatal_error("global initial value must be valid SLEB128");
1055 Globals.push_back(G);
1059 // For now, always emit the memory import, since loads and stores are not
1060 // valid without it. In the future, we could perhaps be more clever and omit
1061 // it if there are no loads or stores.
1062 MCSymbolWasm *MemorySym =
1063 cast<MCSymbolWasm>(Ctx.getOrCreateSymbol("__linear_memory"));
1064 WasmImport MemImport;
1065 MemImport.ModuleName = MemorySym->getModuleName();
1066 MemImport.FieldName = MemorySym->getName();
1067 MemImport.Kind = wasm::WASM_EXTERNAL_MEMORY;
1068 Imports.push_back(MemImport);
1070 // For now, always emit the table section, since indirect calls are not
1071 // valid without it. In the future, we could perhaps be more clever and omit
1072 // it if there are no indirect calls.
1073 MCSymbolWasm *TableSym =
1074 cast<MCSymbolWasm>(Ctx.getOrCreateSymbol("__indirect_function_table"));
1075 WasmImport TableImport;
1076 TableImport.ModuleName = TableSym->getModuleName();
1077 TableImport.FieldName = TableSym->getName();
1078 TableImport.Kind = wasm::WASM_EXTERNAL_TABLE;
1079 TableImport.Type = wasm::WASM_TYPE_ANYFUNC;
1080 Imports.push_back(TableImport);
1082 // Populate FunctionTypeIndices and Imports.
1083 for (const MCSymbol &S : Asm.symbols()) {
1084 const auto &WS = static_cast<const MCSymbolWasm &>(S);
1086 // Register types for all functions, including those with private linkage
1088 // because wasm always needs a type signature.
1089 if (WS.isFunction())
1090 registerFunctionType(WS);
1092 if (WS.isTemporary())
1095 // If the symbol is not defined in this translation unit, import it.
1096 if (!WS.isDefined(/*SetUsed=*/false) || WS.isVariable()) {
1098 Import.ModuleName = WS.getModuleName();
1099 Import.FieldName = WS.getName();
1101 if (WS.isFunction()) {
1102 Import.Kind = wasm::WASM_EXTERNAL_FUNCTION;
1103 Import.Type = getFunctionType(WS);
1104 SymbolIndices[&WS] = NumFuncImports;
1107 Import.Kind = wasm::WASM_EXTERNAL_GLOBAL;
1108 Import.Type = int32_t(PtrType);
1109 Import.IsMutable = false;
1110 SymbolIndices[&WS] = NumGlobalImports;
1112 // If this global is the stack pointer, make it mutable.
1113 if (WS.getName() == "__stack_pointer")
1114 Import.IsMutable = true;
1119 Imports.push_back(Import);
1123 for (MCSection &Sec : Asm) {
1124 auto &Section = static_cast<MCSectionWasm &>(Sec);
1125 if (!Section.isWasmData())
1128 // .init_array sections are handled specially elsewhere.
1129 if (cast<MCSectionWasm>(Sec).getSectionName().startswith(".init_array"))
1132 DataSize = alignTo(DataSize, Section.getAlignment());
1133 DataSegments.emplace_back();
1134 WasmDataSegment &Segment = DataSegments.back();
1135 Segment.Name = Section.getSectionName();
1136 Segment.Offset = DataSize;
1137 Segment.Section = &Section;
1138 addData(Segment.Data, Section);
1139 Segment.Alignment = Section.getAlignment();
1141 DataSize += Segment.Data.size();
1142 Section.setMemoryOffset(Segment.Offset);
1145 // Handle regular defined and undefined symbols.
1146 for (const MCSymbol &S : Asm.symbols()) {
1147 // Ignore unnamed temporary symbols, which aren't ever exported, imported,
1148 // or used in relocations.
1149 if (S.isTemporary() && S.getName().empty())
1152 const auto &WS = static_cast<const MCSymbolWasm &>(S);
1153 DEBUG(dbgs() << "MCSymbol: '" << S << "'"
1154 << " isDefined=" << S.isDefined() << " isExternal="
1155 << S.isExternal() << " isTemporary=" << S.isTemporary()
1156 << " isFunction=" << WS.isFunction()
1157 << " isWeak=" << WS.isWeak()
1158 << " isHidden=" << WS.isHidden()
1159 << " isVariable=" << WS.isVariable() << "\n");
1161 if (WS.isWeak() || WS.isHidden()) {
1162 uint32_t Flags = (WS.isWeak() ? wasm::WASM_SYMBOL_BINDING_WEAK : 0) |
1163 (WS.isHidden() ? wasm::WASM_SYMBOL_VISIBILITY_HIDDEN : 0);
1164 SymbolFlags.emplace_back(WS.getName(), Flags);
1167 if (WS.isVariable())
1172 if (WS.isFunction()) {
1173 if (WS.isDefined(/*SetUsed=*/false)) {
1174 if (WS.getOffset() != 0)
1176 "function sections must contain one function each");
1178 if (WS.getSize() == 0)
1180 "function symbols must have a size set with .size");
1182 // A definition. Take the next available index.
1183 Index = NumFuncImports + Functions.size();
1185 // Prepare the function.
1187 Func.Type = getFunctionType(WS);
1189 SymbolIndices[&WS] = Index;
1190 Functions.push_back(Func);
1192 // An import; the index was assigned above.
1193 Index = SymbolIndices.find(&WS)->second;
1196 DEBUG(dbgs() << " -> function index: " << Index << "\n");
1198 if (WS.isTemporary() && !WS.getSize())
1201 if (!WS.isDefined(/*SetUsed=*/false))
1205 report_fatal_error("data symbols must have a size set with .size: " +
1209 if (!WS.getSize()->evaluateAsAbsolute(Size, Layout))
1210 report_fatal_error(".size expression must be evaluatable");
1212 // For each global, prepare a corresponding wasm global holding its
1213 // address. For externals these will also be named exports.
1214 Index = NumGlobalImports + Globals.size();
1215 auto &DataSection = static_cast<MCSectionWasm &>(WS.getSection());
1218 Global.Type = PtrType;
1219 Global.IsMutable = false;
1220 Global.HasImport = false;
1221 Global.InitialValue = DataSection.getMemoryOffset() + Layout.getSymbolOffset(WS);
1222 Global.ImportIndex = 0;
1223 SymbolIndices[&WS] = Index;
1224 DEBUG(dbgs() << " -> global index: " << Index << "\n");
1225 Globals.push_back(Global);
1228 // If the symbol is visible outside this translation unit, export it.
1229 if (WS.isDefined(/*SetUsed=*/false)) {
1231 Export.FieldName = WS.getName();
1232 Export.Index = Index;
1233 if (WS.isFunction())
1234 Export.Kind = wasm::WASM_EXTERNAL_FUNCTION;
1236 Export.Kind = wasm::WASM_EXTERNAL_GLOBAL;
1237 DEBUG(dbgs() << " -> export " << Exports.size() << "\n");
1238 Exports.push_back(Export);
1239 if (!WS.isExternal())
1240 SymbolFlags.emplace_back(WS.getName(), wasm::WASM_SYMBOL_BINDING_LOCAL);
1244 // Handle weak aliases. We need to process these in a separate pass because
1245 // we need to have processed the target of the alias before the alias itself
1246 // and the symbols are not necessarily ordered in this way.
1247 for (const MCSymbol &S : Asm.symbols()) {
1248 if (!S.isVariable())
1251 assert(S.isDefined(/*SetUsed=*/false));
1253 // Find the target symbol of this weak alias and export that index
1254 const auto &WS = static_cast<const MCSymbolWasm &>(S);
1255 const MCSymbolWasm *ResolvedSym = ResolveSymbol(WS);
1256 DEBUG(dbgs() << WS.getName() << ": weak alias of '" << *ResolvedSym << "'\n");
1257 assert(SymbolIndices.count(ResolvedSym) > 0);
1258 uint32_t Index = SymbolIndices.find(ResolvedSym)->second;
1259 DEBUG(dbgs() << " -> index:" << Index << "\n");
1262 Export.FieldName = WS.getName();
1263 Export.Index = Index;
1264 if (WS.isFunction())
1265 Export.Kind = wasm::WASM_EXTERNAL_FUNCTION;
1267 Export.Kind = wasm::WASM_EXTERNAL_GLOBAL;
1268 DEBUG(dbgs() << " -> export " << Exports.size() << "\n");
1269 Exports.push_back(Export);
1271 if (!WS.isExternal())
1272 SymbolFlags.emplace_back(WS.getName(), wasm::WASM_SYMBOL_BINDING_LOCAL);
1276 auto HandleReloc = [&](const WasmRelocationEntry &Rel) {
1277 // Functions referenced by a relocation need to prepared to be called
1279 const MCSymbolWasm& WS = *Rel.Symbol;
1280 if (WS.isFunction() && IndirectSymbolIndices.count(&WS) == 0) {
1282 case wasm::R_WEBASSEMBLY_TABLE_INDEX_I32:
1283 case wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB:
1284 case wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32:
1285 case wasm::R_WEBASSEMBLY_MEMORY_ADDR_SLEB: {
1286 uint32_t Index = SymbolIndices.find(&WS)->second;
1287 IndirectSymbolIndices[&WS] = TableElems.size();
1288 DEBUG(dbgs() << " -> adding to table: " << TableElems.size() << "\n");
1289 TableElems.push_back(Index);
1290 registerFunctionType(WS);
1299 for (const WasmRelocationEntry &RelEntry : CodeRelocations)
1300 HandleReloc(RelEntry);
1301 for (const WasmRelocationEntry &RelEntry : DataRelocations)
1302 HandleReloc(RelEntry);
1305 // Translate .init_array section contents into start functions.
1306 for (const MCSection &S : Asm) {
1307 const auto &WS = static_cast<const MCSectionWasm &>(S);
1308 if (WS.getSectionName().startswith(".fini_array"))
1309 report_fatal_error(".fini_array sections are unsupported");
1310 if (!WS.getSectionName().startswith(".init_array"))
1312 if (WS.getFragmentList().empty())
1314 if (WS.getFragmentList().size() != 2)
1315 report_fatal_error("only one .init_array section fragment supported");
1316 const MCFragment &AlignFrag = *WS.begin();
1317 if (AlignFrag.getKind() != MCFragment::FT_Align)
1318 report_fatal_error(".init_array section should be aligned");
1319 if (cast<MCAlignFragment>(AlignFrag).getAlignment() != (is64Bit() ? 8 : 4))
1320 report_fatal_error(".init_array section should be aligned for pointers");
1321 const MCFragment &Frag = *std::next(WS.begin());
1322 if (Frag.hasInstructions() || Frag.getKind() != MCFragment::FT_Data)
1323 report_fatal_error("only data supported in .init_array section");
1324 uint16_t Priority = UINT16_MAX;
1325 if (WS.getSectionName().size() != 11) {
1326 if (WS.getSectionName()[11] != '.')
1327 report_fatal_error(".init_array section priority should start with '.'");
1328 if (WS.getSectionName().substr(12).getAsInteger(10, Priority))
1329 report_fatal_error("invalid .init_array section priority");
1331 const auto &DataFrag = cast<MCDataFragment>(Frag);
1332 const SmallVectorImpl<char> &Contents = DataFrag.getContents();
1333 for (const uint8_t *p = (const uint8_t *)Contents.data(),
1334 *end = (const uint8_t *)Contents.data() + Contents.size();
1337 report_fatal_error("non-symbolic data in .init_array section");
1339 for (const MCFixup &Fixup : DataFrag.getFixups()) {
1340 assert(Fixup.getKind() == MCFixup::getKindForSize(is64Bit() ? 8 : 4, false));
1341 const MCExpr *Expr = Fixup.getValue();
1342 auto *Sym = dyn_cast<MCSymbolRefExpr>(Expr);
1344 report_fatal_error("fixups in .init_array should be symbol references");
1345 if (Sym->getKind() != MCSymbolRefExpr::VK_WebAssembly_FUNCTION)
1346 report_fatal_error("symbols in .init_array should be for functions");
1347 auto I = SymbolIndices.find(cast<MCSymbolWasm>(&Sym->getSymbol()));
1348 if (I == SymbolIndices.end())
1349 report_fatal_error("symbols in .init_array should be defined");
1350 uint32_t Index = I->second;
1351 InitFuncs.push_back(std::make_pair(Priority, Index));
1355 // Write out the Wasm header.
1358 writeTypeSection(FunctionTypes);
1359 writeImportSection(Imports, DataSize, TableElems.size());
1360 writeFunctionSection(Functions);
1361 // Skip the "table" section; we import the table instead.
1362 // Skip the "memory" section; we import the memory instead.
1363 writeGlobalSection();
1364 writeExportSection(Exports);
1365 writeElemSection(TableElems);
1366 writeCodeSection(Asm, Layout, Functions);
1367 writeDataSection(DataSegments);
1368 writeNameSection(Functions, Imports, NumFuncImports);
1369 writeCodeRelocSection();
1370 writeDataRelocSection();
1371 writeLinkingMetaDataSection(DataSegments, DataSize, SymbolFlags,
1374 // TODO: Translate the .comment section to the output.
1375 // TODO: Translate debug sections to the output.
1378 std::unique_ptr<MCObjectWriter>
1379 llvm::createWasmObjectWriter(std::unique_ptr<MCWasmObjectTargetWriter> MOTW,
1380 raw_pwrite_stream &OS) {
1381 // FIXME: Can't use make_unique<WasmObjectWriter>(...) as WasmObjectWriter's
1382 // destructor is private. Is that necessary?
1383 return std::unique_ptr<MCObjectWriter>(
1384 new WasmObjectWriter(std::move(MOTW), OS));